It doesn’t seem like this is going to be fixed any time soon (if at all).

Maybe we should maintain another (or the same) site on a different domain
instead?

I don’t think the domain is the issue. There’s just no one to maintain
the site right now. If someone were to set up a mirror on some other
hosting (like GitHub pages, which IronPython now uses) I’m sure the
domain owners at RubyCentral would redirect it.